Air laying apparatus

ABSTRACT

A stream of air carries loose fibers through enclosed ducts and deposits them in a series of equally spaced, substantially identical pads on a continuously moving web as it moves through a generally enclosed chamber. The web and now formed pads exit the chamber through an opening which is sealed by a unitary seal roll. The seal roll is provided with a circumferential cavity corresponding to the contour of the individual pads and is of a circumference equal to the distance between leading edges of successive pads. The seal roll is rotated at a tangential velocity equal to the linear velocity of the web moving under the roll so that a pad passing under the roll mates in the cavity in the roll surface thereby sealing against air leakage into the generally enclosed chamber and compacting the fibers of the pad in a controlled manner.

[ 51 Feb. 27, 1973 AIR LAYING APPARATUS [75] Inventor: Warren R.Furbeck, Knoxville,

Tenn.

[73] Assignee: International Paper Comapny, New

York, N.Y.

[22] Filed: Aug. 23, 1971 [21] Appl. No.: 174,092

I A Related US. Application Data [63] Continuation-in-part of Ser. No.26,002, April 6, 1970, abandoned, which is a continuation-in-part ofSer. No. 672,477, Oct. 3, 1967, Pat. No. 3,509,604.

[56] References Cited UNITED STATES PATENTS 3,518,726 Banks ..19/144.5

Primary ExaminerDorsey Newton Attorney-Fitch, Even, Tabin & Luedeka [57]ABSTRACT A stream of air carries loose fibers through enclosed ducts anddeposits them in a series of equally spaced, substantially identicalpads on a continuously moving web as it moves through a generallyenclosed chamber. The web and now formed pads exit the chamber throughan opening which is sealed by a unitary seal roll. The seal roll isprovided with a circumferential cavity corresponding to the contour ofthe individual pads and is of a circumference equal to the distancebetween leading edges of successive pads. The seal roll is rotated at atangential velocity equal to the linear velocity of the web moving underthe roll so that a pad passing under the roll mates in the cavity in theroll surface thereby sealing against air leakage into the generallyenclosed chamber and compacting the fibers of the pad in a controlledmanner.

6 Claims, 8 Drawing Figures PATENTED FEB 2 7 I973 SHEET 1 OF 3 VACUUMINVENTOR Warren R. Furbeck PATENTED FEBZ 7 I975 SHEET 2 OF 3 INVENTORWarren R. Furbe ck PATENIE mm mm SHEET 30F 3 FIG? INV'ENTOR Warren R.Furbe-ck 1 Ant LAYING APPARATUS This application is acontinuation-in-part of copending application Ser. No. 26,002, filedApr. 6, 1970 now abandoned, entitled Air Laying Apparatus, which in turnis a continuation-in-part of application Ser. No. 672,477, now U.S. Pat.No. 3,509,604 entitled Air Laying System Having a Seal Roll.

This invention relates to an air-laying system for producing a contouredweb or pad from a quantity of loose fibrous'material and moreparticularly to an improved apparatus including a seal roll sealingagainst leakage of air thereby preventing an undesirable movement offibers by the leaking air.

In an air-laying process, a stream of air carries fibers throughsuitable, enclosed ducts and deposits them on a continuously movingpermeable web as it is carried through a generally enclosed formingchamber. The

fibers are filtered from the air stream by the web and may be formed byappropriate methods into a predetermined contour on the traveling web.In one example, a

I diaper pad may be formed by impinging a stream of airborne fibers ofwood pulp onto a continuous web of creped tissue moved in a horizontalpath beneath a forming chamber. The web is moved into and out of thechamber through slots or openings in opposite walls of the chamber, thesealing of at least one of such openings being an objective in thepresent invention. Flow of air for carrying the fibersmay be establishedby appropriate blowers disposed upstream of the web or by suctiondevices disposed downstream of the web or by a combination of these. Ineither event, the stream of air and fibers impinges upon the web and thefibers are filtered from the air stream as the air passes through thepermeable web. The filtered fibers are retained on the web in the formof a mat or pad of loose fibers. The web preferably is disposedhorizontally; the pad also lying in a-horizontal plane.

Because creped tissue and other webs frequently cannot withstand thepressure exerted thereagainst by the impinging flow of air and fibers,such webs are usually supported from beneath by a permeable carrier.Through either partially or completely'blocking the permeability ofportions of such carrier, it ispossible to control the peripheraloutline of the pad and to also control the thickness of the pad over oneor several areas thereof.

U.S. Pat. No. 3,509,604, issued May 5, 1970 to Furbeck and U.S. Pat. No.3,501,813, issued Mar. 24, 1970 to Lee et al., describe a process inwhich fibers of wood pulp are laid on a web formed by a continuous webof creped tissue as part of a process of fabricating a disposable diaperpad which has a central portion thicker than adjacent flanking or sideportions. U.S. Pat. No. 3,501,813 describes three separate rolls, onefor eachof the respective flanking portions and one for the centralportion of the pad, extended to the fibrous pad and slightly compactedthe pad traveling beneath I the respective rolls. All of these threerolls were the same diameter and separately driven at the same speedproviding a tangential velocity equal to the linear velocity of the padand the carrier. Although the adjacentends of the respective rolls weredisposed close to one another, air leaked between them. Also, fiberswere pinched between the adjacent roll ends and began to gather in thespace between the roll ends. This impeded the free turning of the rolls.Eventually these fibers accumulated tothe point where it was necessaryto remove them.

The seal roll described in U.S. Pat. No. 3,509,604, comprises a unitaryroll having selected circumferential grooves conforming to the contourof the pad passing beneath the roll. The mating relation between the padand roll contours effects a seal against air flow therebetween.Appropriate end seals are provided to preclude air leakage in theareasof the roll ends where they are joined to the enclosed forming chamber.Since the grooves in the roll extend uniformly and continuously aroundthe entire circumference of the roll, it is possible to also sealagainst air leakage at the top of the roll by disposing an appropriatelycontoured doctor blade contiguous to the top of the roll, such doctorblade being sealably joined to the enclosed forming chamber. In thismanner, the moving web carrier can pass into or out of the enclosedforming chamber through openings in the chamber without air leakage,such leakage being precluded by the sealing relationship between theroll, the web, the pad, if any, on the web and chamber itself;

In a disposable diaper pad, relatively large quantities of fluid must bequickly distributed and absorbedto prevent flooding and leaking from thediaper. To

achieve maximum absorption and distribution in an inand other prior artknown to the present inventor provide suitable sealing in thoseinstances where the moving pad is continuous and uninterrupted along itslength and of constant width. No known provision has been made in sealrolls for nonuniform width in the pad, nor for interruptions in thelength of the pad.

It is therefore a general object of the present invention to provide animproved air-laying apparatus for continuously forming a series offibrous pads each having a predetermined shape. It is another object toprovide an air-laying apparatus for continuously forming a series offibrous pads of nonuniform width. It is another object to provide anovel construction for a seal roll.

Other objects and advantages of the invention will become apparent fromthe detailed description taken in connection with the accompanyingdrawings in which:

FIG. 1 is a representation of an air-laying apparatus depicting variousnovel features of this invention;

FIG. 2 is an elevational view of an air-laying apparatus embodyingvarious novel features of the present invention;

FIG. 3 is an enlarged, elevational and fragmentary view of the seal rollshown in FIGS. 1 and 2;

FIG. 4 is a fragmentary sectional view taken substantially along theline 4-4 of FIG. 3;.

FIG. 5 is a fragmentary, partially sectioned view of a seal rollconstructed in accordance with another emfor sealing the top of the sealroll;

FIG. 6 is a fragmentary view of a further embodiment for sealing the topof the seal roll;

FIG. 7 is a view of the fibrous pad made by the apparatus of FIG. 1; and

FIG. 8 is an enlarged fragmentary view of a further embodiment of theseal roll shown in FIGS. 1 and 2 and depicting multiple circumferentialcavities on the seal roll.

As shown in the drawings for purposes of illustration, the invention'isembodied in an air-laying apparatus 11 (FIG. 1) which forms a series ofpads 13 (FIGS. 1 and 7) of a predetermined shape from loose fibrousmaterial such as wood pulp fibers. In this instance, each of the fibrouspads is formed with an hour-glass perimeter. In one diaper of 17 incheslength, the wide end portions 15 may be l4 inches in width and thenecked portion 14 may be 5 inches in width. The thickness of the pad maybe uniformly about one-half inch. The present invention, however, is notlimited to any particular size of diaper or pad perimeter or thicknessas the dimensions, perimeter, or thickness may vary with differentembodiments of the invention, except, however, the present invention isdirected toward pads, .each of which is of uniform length and may alsobe nonuniform in width or thickness.

Very generally, the illustrated apparatus employs an air-laying unit 11(FIGS. 1 and 2) which forms the fibrous pads 13. In this instance, acreped tissue web 16 is continuously dispensed from a roll 17 and fedthrough an enclosed chamber 18 through openings in the chamber walls 19,20. The opening in chamber wall 19 serves as an entrance for the web anda carrier 33 into the chamber. This opening may be rectangular and madesufficiently small as will permit the web and its carrierto passtherethrough but will not permit sufficient air leakage to disrupt thepad forming operation within the chamber. If desired, flexible skirts(not shown) may be provided around the periphery ofthis entrancetoincrease the seal against air leakage. Within the chamber 18, fibersare deposited upon the web to produce a series of pads 13 upon themoving web. The present invention is concerned with the production ofseveral individual pads separated one from another along the length ofthe web by a preselected constant distance. The pads are to besubstantially identical. Their width may be constant or it may varyalong the pad length as is depicted by the hour-glass" pad 13 shown inFIGS. 1 and 7.

The air-laying unit 11 is provided with a shredder 23 connected by aduct 27 to a refiner mill 25 which combines its action with that of theshredder to defibrate felted webs of wood pulp (not shown) intoindividual fibers or as close thereto as possible. The individual fibersare carried by an air stream down through a duct 28 to the upper endofan enclosed, forming chamber 18 through which travels a web 16 of crepedtissue on an endless meshed belt carrier 33. A vacuum box 35 is disposedbeneath the upper run of the carrier 33 and is connected in a suitablemanner to a vacuum source to pull the air through the creped tissue weband the meshed belt. The fibers in the air stream are filtered onto theupper surface of the creped tissue web 16 as the air passes through theweb and carrier and into the 'vacuum boxes. Portions of the openingsthrough the meshed belt 33 are blocked, as indicated at 24 in FIG. 1, tolimit air flow through the belt to those areas of the belt where theopenings 26 are left unblocked. As the belt moves through the formingchamber 18, air flows out of the chamber through the tissue web 16 andthe belt 33 through the unblocked openings so that fibers are filteredonto the web 16 in those areas of the web which overlie the unblockedopenings 26 in the meshed belt. The shape of each pad of collectedfibers as well as the distance between succeeding pads is thusdetermined by selectively blocking certain of the openings in the belt.The web and pad move longitudinally from right to left (FIG. 1) throughsuitable slots, such as the slot 32 (FIG. 3) in each of the end walls ofthe enclosed chamber 18. Slot 32 is sealed by a suitable seal roll 37having a formed surface as will be described in detail.

The present invention is of particular utility in producing air-laid,wood pulp fiber pads which have a controlled density and cross-sectionalthickness so as to provide a lightweight, soft and highly absorbent pad.If the fibrous material is too heavily compacted, the pad will notquickly absorb fluids and distribute them with the result that the padand the diaper may be overloaded with fluid which will leak or strikethrough the pad. Also, desirably the. fibers are concentrated in thoseareas where they are most effective in distributing and absorbing bodyexudates. If the pad has portions which are thicker or wider than thatrequired, an excess of fibers is provided beyond that needed forabsorbency and this results in an unnecessary increase in cost of thepad. Hence, a controlled cross-sectional thickness and density isdesired.

In accordance with the present invention, the air-laying apparatus isprovided with an apparatus which provides a controlled thickness andcompaction for the pad by serving as a revolving female die into whichthe pad is fitted as it exits the forming chamber. Such apparatusfurther seals the slot in the chamber wall through which the formed padsleave the air-laying unit 11. To limit the amount of compacting, theseal roll may be lifted as by springs or air cylinders. To assist padformation and seal the exit slot, the seal roll is provided with acircumferential cavity corresponding to the contour of a pad. In apreferred embodiment, it further is of a circumference equal to thedistance between the leading edges of successive pads and is rotated ata tangential velocity equal to the linear velocity of the continuouslymoving web passing beneath the roll and carrying successive pads underthe roll and away from the air-laying unit. The roll also is rotated inregistry with the progressing pads so that each successive pad mateswith the circumferential cavity of the roll as the pad passes under theroll.

Proceeding now with a more detailed description of the invention andwith particular reference to FIGS. 2 and 3, the forming unit 11 issupported by a main frame 39 with the shredder 23 disposed on upperbeams and over the refiner 25. A felted wood pulp (not shown) of apredetermined moisture content is fed to the shredder 23 which chops thewebs into postage-stamp size pieces which are then fed through avertically disposed duct 27 leading down to the. refiner mill 25 whichthen grinds, breaks, or separates the pieces into individual wood pulpfibers or as close thereto as possible. A stream of moving air carriesthe fibers through a duct 28 and into the interior of the generallyboxedshaped, enclosed chamber 18. The latter is generally hollow with anopen, lower end disposed across and closely adjacent to the crepedtissue web 16 and carrier 33 which pass through inlet and outlet slots32 formed in the respective vertical end walls 19, 20 (FIG.3) of thechamber. The slot 32 extends considerably above the web 16 and its upperedge is defined by a wall 44 (FIG. 3). Each of the chamber side walls issealed and connected toa vacuum box 35 below. The vacuum box 35 is aduct connected to a suitable source of suction (not shown). Preferably,the vacuum box 35 is formed by a vertical sidewall 46 (FIG. 3) defininga box-like chamber beneath the forming chamber 18. At the top of thevacuum box is a carrier support 48 in the from of an expanded metalscreen having very wide openings to allow the air to pass easily withoutdisturbing the fiber deposition of the web. As noted hereinbefore,selected ones of the openings through the thickness of the metal screenare blocked to define shaped areas through which the air flows out ofthe chamber. Such blocking is accomplished by any suitable means such asoverlaying a blind belt over the screen with the blind belt havingspaced apart, appropriately contoured openings cut therein. The screenopenings alternatively may be blocked by plugging selected openings witha resin or latex. The seal roll is aligned over the end wall 46 of thevacuum chamber to provide a better sealing action with 1 the vacuumchamber and with the supported pad disposed on and supported by the wall46 at the sealing roll.

The entrained fibers are filtered by the creped tissue web 16 from theair moving into the vacuum boxes. The web 16 is drawn from a largesupply roll 17 and is disposed over the upper surface of the top run ofthe endless carrier belt 33 and moves with the latter through thechamber and then leaves the carrier to move to the next station (notshown) for further processing in forming the disposable diapers. In thisinstance, the web 16 is approximately 14 inches in width and the endlessmesh belt 33 is of substantially equal width. The belt 33 is trainedabout a drive roll 49 rotatable about a generally horizontal axis anddriven by a chain 51 extending to a gear unit 53 which in turn is drivenby a drive shaftof the diaper-making machine (which is not shown). Themesh belt 33 extends from the drive roll 49 to an idler roll 55 and theupper run of the belt is disposed in a generally horizontal plane fortravel through the air-laying unit. A pair of belt tension rolls 57 holdthe endless carrier belt 33 at the proper tension. Fibers commencecollecting on the web 16 as each portion of the screen having unblockedopenings enters the chamber 18 underneath the continuously moving web'.As the web and carrier move together through the chamber, more fibersare collected on the web to form a pad of the desired thickness. Uponthe web and screen leaving the chamber, the web carries the pad forwardfor further processing and the screen passes through a lower run andreturns to the chamber entrance.

To seal slot 32 against the entry of air into the chamber, which is.below atmospheric pressure, an outlet seal roll is provided for theenclosed chamber 18. As best seen in FIGS- 3 and 4, seal roll 37 ismounted for rotation by stub shafts 61 disposed in a pair of bearings 63carried by support arms 65. The rotational axis of the seal roll isdisposed generally horizontally above and parallel to the web 16 and isdisposed normal to the path of the web travel.

Adjacent the respective ends of the seal roll 37 are end seals 69 (FIGS.3 and 4) of generally L-shaped configuration each with a verticallyextending leg 70 fastened to the housing wall 20 adjacent the verticalsides of slot 32. The end seals 69 project outwardly from the housingwall20 to positions closely adjacent the radial end walls of thesealroll 37. Extending across the top of the seal roll 37 is a resilientroll 71. The resilient roll extends outwardly from the wall 20 intorolling engagement with the surface of the rotating seal roll and isfixedly biased against the seal roll so as to force a portion of theresilient roll into the circumferential cavity formed in the seal roll.The top of the resilient roll' 71 may be sealed against air flow intothe forming chamber by a doctor blade or skirt, preferably flexible toaccommodate vertical movement of roll 71, sealably joined to the chamberwall 20 and in sliding contact with the top of roll 71. Thus, theresilient roll and the end seals prevent sideways and overhead entranceof air or the loss of fibers from the slot 32. Because the lower surfaceof the roll 37 is in contact with the pad and web, it alleviates theloss of air pressure at the interface of the seal roll and the padreduces any inward flow of ambient air to a volume and flow rate whichwill not disturb the velocity profile of the air stream within theforming chamber 18. That is, a large leakage of ambient air beneath theseal roll and into the chamber could roll fibers from the pad back intothe chamber and also disrupt the air stream profile within the chamberand thereby disrupt the pad contour.

I In the preferred embodiment of the invention, the seal roll alsofunctions as a web feeding roll in that the web 16 is gripped in the nipbetween the seal roll and the belt 33 and they combine to strip the webfrom its supply roll 17 and pull the web through the air-laying unit. Tofeed the creped tissue web 31 without wrinkling or tearing, the sealroll may be formed with a resilient layer 77 (FIG. 5) for pressingagainst the web 16 and belt 33. More specifically, the seal roll mayhave a layer of rubber one-eighth inch thick' fixed about a cylindricalmetallic sleeve 78 for the seal roll.

The axial end portions of the seal roll are of equal diameter and arerotated at the same peripheral speed to feed the web 16. To rotate theroll 37, there is provided a drive train which includes a sprocket 79(FIG. 4) fixed to stub shaft 61 and a driving chain 81 extending fromthe sprocket 79 to another sprocket 83 fixed to a support shaft 85journaled in bearings 87 (FIG. 4) on the lower end of vertical framemember 89. The free end of support shaft 85 is provided with a worm gear91' which is meshed with a suitable gear 93 carried on a horizontaldrive shaft 95 extending longitudinally of the carrier 16. The shaft 95is connected to and driven by a gear box 96 (FIG. 2) driven by a chain97 extending to the drive sprocket for the carrier drive roll 49.Because the carrier 33 and the seal roll 37 are both driven by the gearunit 53, the speed of the carrier may be correlated with the rotationalspeed of the seal roll such that the tangential velocity of the sealroll engaging the web 16 matches the linear velocity of the carrier 33,hence the linear velocity of web 13.

In accordance with the preferred embodiment of the invention, the sealroll 37 is in the: form of a unitary roll having a circumferentialcavity of about one-half inch uniform depth and an arcuate length equalto the linear dimension of the pad 13. A land 22 on the rollcircumference defines the beginning and end of cavity 21. The arcuatelength of this land corresponds to the linear spacing between successivepads 13 deposited on the web 16 so that as the seal roll is rotated at atangential velocity equal to the linear velocity of the web 16 and inregistry with the pads passing beneath the seal roll, one pad passesbeneath the seal roll per each rotation of the roll, such pad matingwith the cavity 21 inthe roll.

It has been found that the cavity 21 in the roll surface is particularlyeffective in shaping the pad fibers and establishing a controlledthickness. The slight compaction of the fibers by the roll assures asmoother upper surface and enhances the coherence of the fibrous padwhich is of primary importance to the absorption characteristic of thepad and also of importance in providing a diaper which does not depositfibrous matter upon the body of an infant.

In this instance, the pressure of the seal roll on the pad is regulatedby biasing means which are in the form of individual attached scales 107such as the common grocery scales comprising an elongated housingencasing an internal spring having an external load indicator means. Thescales are fastened at their lower ends to the pivotally mounted bracketarms 65 for the seal rolls and attached at upper ends to a horizontallydisposed, stationary frame member 108 (FIG. 2). The scales areadjustably mounted so that the force with which the roll engages the padcan be limited to a predetermined portion of the weight of the roll 37and its pivot arm 65. In the preferred embodiment of the invention,,theseal roll applies a light even pressure to the pad 13 just sufficient toembed the pad in the roll cavity, therebystopping any large volume ofambient air from moving under the roll and imparting the desired degreeof compaction to the pad.

To prevent pickup of fibers on the seal roll from the fibrous pad, theroll may have an outer layer of plastic material disposed on theresilient layer 77. A film of 0.0005 inch of polytetrafluoroethylene assold under the trademark Teflon has been applied to the outer surface ofthe roll and has worked satisfactorily.

To control the amount of pressure exerted by the roll on the pad andthereby the amount of fiber compaction by seal roll 37, the seal roll ispivotally mounted for pivoting about a support shaft 85 and is liftedupwardly by an associated spring scale 107. The latter lifts apredetermined portion of the weight of the roll so that the roll engagesthe pad with a light yet predetermined force.

It will be appreciated that the seal roll may be provided also at theentrance opening of chamber 18. Because this entrance seal roll sealsagainst the web 16 only, it is not provided with a cavity and has anuninterrupted cylindrical surface and a uniform diameter across its fulllength.

As an aid to understanding the invention, a brief description of theoperation of the invention is provided. The creped tissue web 16 isdisposed in the nip between the seal roll 37 and the upper surface ofthe continuous carrier 33. The seal roll engages the outer side edges ofthe creped tissue web and as the roll rotates, it and the carrier 33strip the web from the supply roll 17.

As the web 16 passes through the unit 11, air-borne fibers move throughthe duct 27 into the enclosed chamber 29 and deposit on the web to forma pad of fibers. The air stream carrying the fibers moves through theweb 16 and the meshed carrier 33 into the vacuum box 35 beneath the weband carrier.

The seal roll 37 is driven by shaft which, in turn, is driven by thedrive 53 for the carrier 33 so that the seal roll portions engaging theweb 16 have a tangential speed equal to the linear speed of the carrier33.

The seal roll extends into engagement with the fibrous pad 13 on the web16 to provide a lower seal preventing the loss of air pressure andfibers along the carrier and web from the slot 32 in the housing 29. Atthe opposite ends of the seal roll, end seals 69 are fixed to theenclosing chamber wall 20 and extend to the radial end faces of theroll. The slot 32 is further sealed at the top of the roll by theresilient roll 71 engaging the seal roll 37. The top of the resilientroll 71 is sealed by a doctor blade 68, preferably flexible, sealablyjoined to the wall 20 and extending outwardly from the wall to contactthe resilient roll 71.

Best results are obtained by the direct positive driving rotation of theseal roll 37 by the shaft 95. Less satisfactory, but adequate resultshave been obtained without using such a positive drive. For instance,the seal roll may be rotated solely by the carrier 33 against which theroll is biased. Thus, the roll will, except for any slippage, have atangential velocity equal to the linear velocity of the carrier 33.

From the foregoing it will be seen that the airlaying apparatus providesa pad with an improved outer surface, a controlled cross-sectionalthickness, and a controlled degree of compaction. Also, the seal rollconstruction may be greatly simplified and easily driven through asimple driving arrangement. Although the seal roll 37 is shown anddescribed in connection with a single air-laying unit, it will beappreciated that this roll could be also employed in a tandem air-layingapparatus where the pad is formed by sequential air-laying operationsperformed by a pair of tandem units rather than by a single unit.

Because the circumference of roll 37 is provided with both a cavity anda land, it will be recognized that the top of the roll cannot be sealedby a rigid member having a leading edge contoured to sealably engage therotating seal roll. Accordingly, in the present invention, the top ofthe roll preferably is sealed by a further roll 71 formed of a resilientmaterial or having a resilient surface coating or layer. This latterroll is rotatably mounted adjacent the uppermost portion of the slot 32and with its axis of rotation parallel to the rotational axis of theseal roll 37. The resilient roll 71 is fixedly biased against the sealroll and rotated therewith conveniently by frictional engagement betweenthe rolls. As the rolls rotate together, the resilient surface of roll71 expands into the cavity 21 in the circumference of the seal roll andyields to accommodate the land 22 as well as the end portions of theseal roll surface, thus maintaining continuous sealing engagement withthe rotating seal roll along a line extending between the opposite endsof the seal roll 37. The opposite ends of the resilient rolls are sealedby plates 63 as described for sealing the ends of the seal roll 37. Thetop portion of this resilient roll 71 is sealed against air flow intothe forming chamber by means of a doctor blade 68, sealably joined tochamber wall 20 and extending outwardly therefrom to engage the top ofthe roll 71 in sliding and sealing contact. Preferably, the doctor blade68 is flexible so as to accommodate slight vertical movements of theseal roll 37 as discussed hereinbefore.

In a further embodiment (FIG. 6) for sealing the top of the seal roll37, there is provided an elongated plate 30 secured to the wall 20 ofthe chamber 18 and having a plurality of fingers 31, which arepreferably flexible,

depending from its leading edge to slide over the outer surface of therotating seal roll. These fingers are spaced very close to one anotheralong the edge of the plate so as to prevent air flow between fingers.As the seal roll rotates, individual ones of these fingers may fall intothe cavity 21 in the seal roll surface due to gravitational pull or beforced therein by biasing means (not shown). In either event, thefingers slide upon the seal roll surface, either in or out of the cavityas the case may be, and seal against air leakage into the chamber 18through the slot 32.

It will be appreciated that the seal roll may be provided with two ormore circumferential cavities as distinguished from a single cavity. Asea] roll 37 having multiple cavities 21a and 21b is shown in FIG. 8. Amultiple-cavity seal roll may possess a circumference equal to thelinear distance between the leading edges of successive pads passingbeneath the rotated roll and be rotated at an appropriate tangentialvelocity as will cause successive pads to mate with successive cavitiesin the seal roll. For example, for a given linear velocity of padspassing beneath the seal roll, a three-cavity roll having acircumference equal to the linear distance between the leading edges ofsuccessive pads may be rotated with a tangential velocity one-third ofthat of a single-cavity seal roll having the same diameter.Alternatively, a three-cavity seal roll could be made with acircumference three times the linear distance between the leading edgesof successive pads and be rotated with a tangential velocity equal tothat of a single-cavity seal roll having a circumference equal to thelinear distance between the leading edges of successive pads, assuming agiven linear velocity of the pads.

While a preferred embodiment has been shown and described, it will beunderstood that there is no intent to limit the invention by suchdisclosure but, rather, it is intended to cover all modifications andalternative constructions falling within the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. in an apparatus for continuously air laying a series of substantiallyidentical fibrous pads each of uniform length spaced one from another apreselected constant distance on a moving carrier, said apparatusincluding at least one chamber in which fibers are carried by an airstream and are deposited on said carrier, said chamber having an openingthrough which said carrier and pads leave said chamber, the improvementcom prising a unitary seal roll mounted for rotation about an axisdisposed transversely of the movement of said pads and disposed to sealsaid opening by engaging successive ones of said ads and closing saidopening at least one crrcumferen ral cavity in said roll extending lessthan completely around the roll circumference which when laid flatcorresponds to the contour of individual ones of said pads, at least oneland on the circumference of said roll defining the beginning and end ofsaid cavity, and means for rotating said roll about its axis at atangential velocity relative to the linear velocity of said pads on saidcarrier whereby said cavity is in registry with successive forwardlymoving pads and successive pads mate with and enter said cavity as saidroll is rotated and said pads are moved forwardly.

2. The apparatus of claim 1 wherein the circumference of said seal rollequals the linear distance between the leading edges of successive padson said carrier and the tangential velocity of said seal roll equals thelinear velocity of said pads on said carrier.

3. The apparatus of claim 1 wherein said seal roll includes multiplesubstantially identical circumferential cavities separated bysubstantially identical lands on the circumference of said roll.

4. The apparatus of claim 1 wherein said circumferential cavity of saidseal roll is of nonuniform width.

5. The apparatus of claim 1 and including elongated resilient sealingmeans having its longitudinal axis parallel to said seal roll axis anddisposed contiguous to and in sealing engagement with said seal roll ina region of said seal roll other than the region where said seal rollsealably contacts said pads to preclude air leakage between said sealroll and said chamber in such other region.

6. The apparatus of claim 5 wherein said elongated resilient sealingmeans comprises a. roll having at least a resilient surface and disposedin rolling contact with said seal roll.

1. In an apparatus for continuously air laying a series of substantiallyidentical fibrous pads each of uniform length spaced one from another apreselected constant distance on a moving cArrier, said apparatusincluding at least one chamber in which fibers are carried by an airstream and are deposited on said carrier, said chamber having an openingthrough which said carrier and pads leave said chamber, the improvementcomprising a unitary seal roll mounted for rotation about an axisdisposed transversely of the movement of said pads and disposed to sealsaid opening by engaging successive ones of said pads and closing saidopening, at least one circumferential cavity in said roll extending lessthan completely around the roll circumference which when laid flatcorresponds to the contour of individual ones of said pads, at least oneland on the circumference of said roll defining the beginning and end ofsaid cavity, and means for rotating said roll about its axis at atangential velocity relative to the linear velocity of said pads on saidcarrier whereby said cavity is in registry with successive forwardlymoving pads and successive pads mate with and enter said cavity as saidroll is rotated and said pads are moved forwardly.
 2. The apparatus ofclaim 1 wherein the circumference of said seal roll equals the lineardistance between the leading edges of successive pads on said carrierand the tangential velocity of said seal roll equals the linear velocityof said pads on said carrier.
 3. The apparatus of claim 1 wherein saidseal roll includes multiple substantially identical circumferentialcavities separated by substantially identical lands on the circumferenceof said roll.
 4. The apparatus of claim 1 wherein said circumferentialcavity of said seal roll is of nonuniform width.
 5. The apparatus ofclaim 1 and including elongated resilient sealing means having itslongitudinal axis parallel to said seal roll axis and disposedcontiguous to and in sealing engagement with said seal roll in a regionof said seal roll other than the region where said seal roll sealablycontacts said pads to preclude air leakage between said seal roll andsaid chamber in such other region.
 6. The apparatus of claim 5 whereinsaid elongated resilient sealing means comprises a roll having at leasta resilient surface and disposed in rolling contact with said seal roll.